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Title:	Introgression of sheath blight resistance qtls into a new high yielding rice (oryza sativa l.) variety UKMRC 2
Authors:	Md Kamal Hossain (P63028)
Supervisor:	Wickneswari Ratnam, Prof. Dr.
Keywords:	Rice sheath blight Rice disease Breeding Dissertations, Academic -- Malaysia Universiti Kebangsaan Malaysia -- Dissertations
Issue Date:	19-Nov-2015
Description:	Rice sheath blight (SB) caused by a soil-borne necrotrophic fungal pathogen Rhizoctonia solani Kühn [teleomorph: Thanatephorus cucumeris (A.B. Frank)], is an economically important disease of rice. Breeding for durable resistance is a viable option to combat the disease efficiently. R. solani field isolates were collected from Kota Baharu, Kelantan, Malaysia. Infected rice sheaths were used to isolate R. solani using PDA culture method. Identification of the pathogen and subsequent virulence tests were done in greenhouse infection using three rice cultivars i.e. MR 219, UKMRC9, and O. rufipogon. Severe SB infestations were observed from all the three cultivars used. The fungal isolate was further confirmed as R. solani via ITS-rDNA region sequencing, microscopic observations, and morphological investigations. rDNA sequence of ITS region was submitted into NCBI GenBank which has been assigned the accession number, 'KF312465'. Nine rice cultivars including six moderately resistant cultivars, namely Teqing, Jasmine 85, Tetep, Pecos, Azucena and Taducan, one susceptible local cultivar, MR 219, and two new varieties, UKMRC 2 and UKMRC 9 were screened in greenhouse using micro-chamber and mist-chamber methods to identify resistant donors. Disease infestation was evaluated as disease severity index (DSI) based on 0 to 9 SB scale for relative lesion height (RLH) and Visual rating (VRT). Results indicated that Tetep, was the most resistant cultivar followed by Teqing with the lowest DSI 3.0 (VRT) and 4.0 (VRT and RLH), respectively. Nevertheless, UKMRC 2 showed the highest level of susceptibility with a mean DSI of 6.67, while MR 219 was at 7.22. IR65482-4-136-2-2, MR 219-4 and MR264 were found to have improved resistance potentials. Plant height and flag leaf angle were found as significantly correlated with SB resistance. To understand association among morphological traits and SSR marker alleles, UPGMA based cluster analysis and principal component analysis (PCA) were performed with specific attention to nine morphological traits and 17 QTL-linked SSR markers. Multivariate analyses revealed that morphological traits such as flag leaf length and plant compactness were found to be the most discriminatory factors between resistant and susceptible genotypes. Similarly, SSR markers (allele) such as RM201 (182), RM257 (141), RM205 (102), RM439 (282), RM6971 (196), and RM426 (156) were found in association with SB resistance. Identified donors, Teqing and Tetep were crossed to introgress resistance QTLs into the susceptible cultivar, UKMRC 2. Two BC1F1 populations, BC1F1 TQ and BC1F1 TT were developed through backcrossing between UKMRC 2 and Teqing, and UKMRC 2 and Tetep, respectively. Field evaluations of SB were performed for both the BC1F1 generations at Q-terrace of Universiti Kebangsaan Malaysia, Bangi, Malaysia. Results showed sufficient segregations in plant height, days to heading, tiller numbers and in disease reactions. A total of 14 out of 414 BC1F1 progenies were detected as 'resistant' to 'moderately resistant' genotypes with 0.0 to 3.0 SB score. QTL analysis was performed using composite interval mapping (CIM) at 15 cM fixed window with co-factor dropping method. Results indicated that the QTL qSB-9TQand qSBR11-1TT were successfully introgressed into high yielding and SB susceptible new rice variety UKMRC 2 genomic background which had been authenticated with significant LOD scores (3.25 & 3.66). Thus, this present research validated and confirmed the suitability of application of marker assisted introgression breeding for sheath blight resistance in rice.,Ph.D.
Pages:	154
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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